Which letter is represented by the phonetic alphabet term "echo"?

The phonetic alphabet, often referred to as the NATO phonetic alphabet, is used to clearly communicate letters over radio and telephone transmissions where clarity is crucial. In this system, "echo" represents the letter E. The purpose of using phonetic terms is to eliminate confusion that might arise from similar-sounding letters or poor communication conditions.

In this case, the term "echo" directly corresponds to the letter E, making it the correct answer. Each phonetic term in the alphabet corresponds to a specific letter, ensuring that communication is standardized and efficient, especially in military and aviation contexts.